This invention relates to electrical apparatus provided with heat pipe cooling means, and more particularly, to electrical apparatus provided with wells to removably secure heat pipes to the electrical apparatus.
It is well-known to those skilled in the art that electrical apparatus, such as distribution transformers and the like, generate considerable heat during operation. It is also well-known that it is necessary to dissipate this heat to prevent the destruction of the electrical apparatus. Normally, the heat is dissipated by air cooling. For example, by pole or pad mounting of the electrical apparatus. When such apparatus is placed below ground, normally vaults are utilized. Grills are provided over the vaults in order to circulate cooling air into vaults and about the electrical apparatus. In all such instances, the size of the container or enclosure for electrical apparatus must provide sufficient area in contact with the air to provide adequate cooling.
When the electrical apparatus is directly buried in the ground, the cooling depends solely on the conduction of the heat from the enclosure of the electrical apparatus through the surrounding soil and to the atmosphere above. In general, cooling by this means is less efficient, thus, larger tanks or enclosures have been required for buried transformers when compared to the enclosures of electrical apparatus of the same rating cooled by air. For buried transformers, since the heat must be conducted through the soil to the atmosphere, the top of the enclosure is the closest surface to the soil-atmosphere interface and thus would be the most efficient heat transfer surface. However, the air space within the transformer enclosure greatly restricts the heat transfer from this surface.
Recently, it has been suggested that buried tanks should be substantially elongated to provide greater surface area in contact with the ground or soil; where the tank is positioned in a substantially constant moisture area. See U.S. Pat. No. 3,443,157. The elongation of the tank is said to improve movement of the insulating fluid and provide better contact between the moving insulating fluid and the entire outer wall of the tank, thus, improving heat conduction. However, the elongated transformer tank depends entirely on the heat conduction between the tank wall and the ground. Thus, the cooling of such device will be dependent on the total surface area of the tank which is in contact with the ground.
It has recently been discovered that more efficient cooling of electrical apparatus can be obtained through the use of heat pipes. Using the heat pipe particularly as a portion of the enclosure of the electrical apparatus will provide greater cooling while not being as dependent on the overall surface area of the electrical apparatus enclosure. Such a transformer is disclosed in application Ser. No. 544,037, filed Jan. 27, 1975, for Electrical Apparatus With Heat Pipe Cooling, in the names of Paul L. Waldon and Ronald E. Bennett, the inventor herein, and assigned to the same assignee as this invention.
While the above application provides one solution to the cooling of transformers, especially buried transformers, it does require that the heat pipe be constructed as a portion of the transformer enclosure. This to some extent minimizes the efficiency of the heat pipe. In order to provide for more efficient heat pipes for cooling of electrical apparatus, it has been found desirable to provide a means for removably attaching heat pipes to electrical apparatus, particularly buried distribution transformers. This would enable a more efficient heat pipe construction since the heat pipes could be shipped separately from the apparatus and attached to the apparatus at the site where the apparatus is to be installed; for example, buried. This will, of course, provide ease in the shipping, handling and storage of both the apparatus and the heat pipe for the manufacturer as well as the customer. Of course, it will also provide for the use of more efficiently constructed heat pipes.
It is, therefore, a principal object of this invention to provide for the removable attachment of heat pipes to electrical apparatus.
A further object of this invention is to provide wells in electrical apparatus which will receive heat pipes to provide improved cooling of such electrical apparatus.